Rod and cone visual pigments will be measured and identified in a number of new species of vertebrate by single cell microspectrophotometry. Special attention will be given to birds, the class so far least investigated, to learn whether a multiple pigment system mediates color vision and whether there are rod-pigment-containing cones. Membrane and transduction work will include further evaluation of Ca ions release and binding to rod membranes, determination of the source of three phases of rod outer segment birefringence change generated by light and attempts to identify changes in rhodopsin and membrane conformation not signalled by changes in visible light absorption.